ML20245J301
| ML20245J301 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/23/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20245J293 | List: |
| References | |
| NUDOCS 8906300264 | |
| Download: ML20245J301 (4) | |
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UNITED STATES
'! A Ti NUCLEAR REGULATORY COMMISSION
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%......f ENCLOSURE 2~
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMEN 0 MENT NO.
TO FACILITY OPERATING LICENSE NO. DPR-77 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNIT 1 DOCKET N0. 50-327
1.0 INTRODUCTION
By: letter dated June 16, 1989, the Tennessee Valley Authority (TVA or the licensee) requested an exigent amendment to the Technical Specifications (TS)'
for the Sequoyah Nuclear Plant, Unit 1.
If approved, the amendment would ~
" temporarily revise Specification 3.1.3.2, " Position Indication System-Operating,"
to allow the licensee to use an alternative method to determine the position of a control' rod in a shutdown bank, where the rod 'has an inoperable rod position indicator (RPI), from that specified in the TS.
The change would apply only for Unit 1 until the next outage of sufficient duration when maintenance can be performed to repair the inoperable RPI but no later than the Unit 1 Cycle 4 refueling outage scheduled for April of 1990.
The change would also state that the provisions of Specification 3.0.4 do not apply so that the licensee ~may change reactor modes during this time period with the RPI inoperable.
As discussed below, the Commission determined, pursuant to 10 CFR 50.91, that this amendment should be implemented as soon as possible.
A-Public Notice that the NRC staff proposed to amend the operating license of Unit I was published in the Chattanooga News-Free Press and the Chattanooga Times on Wednesday, June 21, 1989.
i 2.0 EVALUATION The control rods are divided into two categories:
control and shutdown.
The 3
control category rods are used to compensate for reactivity changes due to
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variations in operating conditions of the core. The shutdown category rods are i
fully withdrawn from the core-during startup and remain fully withdrawn until the unit is shut down.
3 An RPI for a Unit 1 control rod in shutdown bank D has been declared inoperable by the licensee because of voltage fluctuations in the analog RPI instruments-tion channel.
Action a.1 of Specification 3.1.3.2 requires the determination 3
of the position of the non-indicating rod indirectly by the moveable incore
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detectors at least once every eight hours while the RPI is inoperable.
The 1
licensee has been using these detectors since the RPI was declared inoperable.
8906300264 890623 PDR ADOCK 05000327 P
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. r The use of the incore detector system to comply with Action a.1 increases the use 'of the incore detector system from once each month to 90 times each month, significantly increasing the wear on the associated thimble tubes.
The mcVeable incore detectors nove through thimble tubes.
TVA has stated that it has determined that Sequoyah, Unit 1 must be shut down to repair the inoperable RPI.
This increased use of the incore detector system and the resulting wear on the thimble tubes are nonconservative.
The concerns for the wear on'these tubes were identified in NRC Bulletin 88-09, " Thimble Tube Thinning In i
Westinghouse Reactors," issued on July 26, 1988.
Excessive wear of the l
thimble tubes results in a degradation of the reactor coolant system pressure boundary and can create the possibility of a non-isolable leak of reactor coolant.
The thimble tubes are part of the reactor coolarit pressure boundary.
TVA has determined that the objectives of Action a.1 of Specification 3.1.3.2 can be met with an inoperable RPI in a shutdcwn bank without subjecting. the incere thimble tubes to unnecessary additional. wear.
TVA will install a strip chart recorder to track the output voltage of the stationary gripper coil on the non-indicating rod (s) and verify at least once every eight hours that the non-indicating rod (s) has not changed position. This eight-hour surveillance period is consistent with the current operational requirements in Action a.1 for rud position determination.
If the coil has changed state, a determina-tion of the non-indicating rod (s) position will be made by use of.the moveable incore detectors.
In addition, at least once every 31 days, a full-core flux map (of the Unit 1 core will be performed and the position of any non-indicating rod s) will be oetermined using the moveable incore detectors.
This is to determine operability of the full-length control rods as required by Surveillance Requirement 4.1.3.1.2.
These periodic surveillance will provide additional assurance that the non-indicating rod (s) is in the expected position.
The control rods are moved up cr oown by repetitive action of the moveable gripper coil, stationary gripper coil and lif t coil.
During plant operation, the stationary gripper coil holds the control rod in a static position.
For the control rod to move, the output voltage on the stationary gripper coil must change from being "off" to being "on" to being "off" again.
This change would be registered as a change in the output voltage which would be recorded on the strip chart recorder.
This method of determining if the non-indicating control rod has moved is as reliable as the current specified method of deter-mining where the control rod is using the moveable incore detectors.
If the J
non-indicating control rod has moved, the licensee will locate the control red
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using the current specified method.
The frequency of surveillance on the j
non-indicating control rod remains the same frequency specified in Action
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statement a.1, at least once per every eight hours.
j Based on the above, the staff concludes that the proposea change is acceptable.
This change applies only to control rods in a shutdown bank and does not change the requirement in Action a.1 that only one roc' position indicator per bank may be inoperable.
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3.0. EXIGENT CIRCUMSTANCES The NRC staff has determined that this change should be implemented as soon as possible.
The amendment would permit the licensee to continue determining the position of the control rod, in the shutdown bank with the inoperable RPI, without subjecting the thimble tubes to excessive wear.
The proposed changes have no adverse effect on safety and would be beneficial to overall plant safety.
Excessive weer of the thimble tubes results in a degradation of the i
reactor coolant system pressure boundary and can create the possibility of a R
non-isolable leak of reactor coclant.
The proposed change will reduce the likelihood of the reactor coolant boundary being compromised and should be permitted with minimum delay.
Consequently, the NRC staff determined that exigent circumstances exist which justify reducing the public notice period normally provided for licensing amendments and proposed, in the Public. Notice published on June 21, 1989, to issue the amendment at the close of business on June 23, 1989.
4.0 FINAL N0 SIGNIFICANT HAZARDS CONSIDERATION The licensee has evaluated this proposed change with regard to the determination of wnether or not a significant hazards consideration is involved. Operation af Sequoyah, Unit 1 in accordance with the proposed amendment will not involve e significant increase in the probabliity or consequences of an accident previously evaluated.
The proposed change to the Sequoyah, Unit 1. Technical Specifications is to provide on alternative method for verifying shutdown rod position in the event the associated RPI becomes inoperable.
The proposed change meets the intent of the current specification in that it ensures verification of position of the shutdown rod (s) once every eight hours.
The proposed change provides only an alternative method of monitoring shutdown rod position and does not change the assumption or consequences of any previously evaluated accident.
Therefore, the proposeo change will not increase the probability or consequences of any previcusly evaluated accident.
The proposed change will not create the possibility of a new or different kind of accident from any previously analyzed.
As describeo above, the proposed
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change provides only an alternative method of determining shutdcwn rod (s) g position. The proposed change does not affect the reactor protection system or the full-length rod control system.
Therefore, the proposed change does not create the possibility of a new or different kind of accident from any t
previously analyzed.
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The proposed change will nct involve a significant reduction in a margin of safety.
The Bases of Specification 3.1.3.2 state that the operability of the control RPIs is required to determine control rod positions and thereby ensure compliance with the control rod alignment and insertion limits.
The proposed change does not alter the requirement to determine rod position but J
provides an alternative and reliable method for determining the position of the affected rod (s).
Therefore, the proposed change does not reduce the margin of safety.
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> 'The requested amendment has'been evaluated against the standards in 10 CFR 50.92 and.the NRC staff has determined that the requested amendment. involves tw significant hazards considerations. The changes do not affect the.proba-bility or consequences of'any accident previously considered, create the -
possibility of an. accident of a different kind, nor decrease any margin of safety.
5.0 CONSULTATION WITH THE STATE l
' On June 16, 21, and 23, 1989, the State of Tennessee was contacted by tele-phone and the proposed amenament was discussed.
A copy'of.the Public. Notice
' issued by the staff with its preliminary determination of no significant hazards. consideration was telecopied to the' State.
On June 23, 1989, the State contact had'no comments on this determination.
6.0 RESPONSES FROM THE PUBLIC In the Public Notice for this proposca action,- the NRC staff stated that all' comments received by close of business on June.23,1989 would.be considered in reaching a final determination of no significant hazards consideration.
No comments were received by the staff before the' close of business.on June 23, 1989.
7.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a' change to a requirement with respect to the install-ation or use of a facility component located within the restricted area as defined in 10 CFR Part-20.
The staff'has determined that the amendment involves no significant increase in the amounts, and.no significant change in the types, of any effluents that may released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding.
Accordingly, the emendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
8.0 CONCLUSION
The staff has concluded, based on the considerations ciscussed above, that:
2 (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations, and the issuance of the amendments will not be inimical to the common defense and security nor to the health and safety of the public.
Principal Contributor:
J. Donohew j
Dated:
June 23, 1989
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